As is well known, cutting machines often referred to as coal augers or drum shearers are used worldwide in mining operations for excavating coal seams. They are used in underground workings together with a conveyor, designed as a chain conveyor, which can be advanced in the direction of excavation and are designed in such a way that they straddle the conveyor in the manner of a portal with their machine body. In this case, the cutting machines are supported and guided on both sides of the conveyor on guide rails arranged on the conveyor.
The modern cutting machines are moved along the conveyor with the aid of a pin-type drive during their excavation run. In this case, it is usual to arrange a pin drive element on the side remote from the coal face, i.e. on the stowing side of the conveyor, which element comprises toothed or pin-type racks or preferably a pin drive chain. In this case, the cutting machine has at least one gearwheel or pin wheel which is driven by a drive and engages in the pin-type rack mounted on the conveyor or in the horizontal chain links of the pin drive chain (DE-C-25 30 754, DE-A-29 38 446, FR-C 2 523 639).
It is usual to guide the cutting machine on that side (generally the stowing side) of the conveyor where the pin drive element or the pin drive chain is located by means of guide shoes on guide strips which, in this case, are attached laterally to the conveyor, machine guiding in the vertical and lateral direction being brought about with the aid of the guide shoes. In this case, it is also known to attach the guide shoes to the cutting machine or to guide arms thereof by means of horizontal transverse bolts so that they can pivot up about the bolt to a limited extent, so that they are capable of adapting to the path of the conveyor which is usually not horizontal. In this case, guide shoes are used, for example, which engage around the pin-type racks from above and below approximately in the manner of a hook, and which are attached to the cutting machine or its machine body with spacing above the pin-type racks so as to be pivotable about the horizontal transverse bolts (DE-C-25 52 085, DE-C-26 26 291, DE-A-29 25 240). However, it is also known to attach bearing rails to the conveyor on the stowing side, in which rails the pin drive chain is disposed, and which at the same time form guide strips for the guide shoes (FR-C 2 523 639).
A disadvantage of these known arrangements is that, although the guide shoe, as a result of its pivotability about the transverse bolt, provides compensation when the floor is not flat, the guide shoe can nevertheless become clamped on the guide strip while the cutting machine is moving, if the guide strip does not extend precisely in a straight line, but assumes a slightly curved course, for example when advancing the individual conveyor pans of the conveyor. In this case, constraining forces may occur between the guide shoe and the guide strip, which forces are transmitted to the cutting machine and result in increased wear.